Need help on bench and install frappe framework installation

bench init --frappe-branch develop --frappe-path https://github.com/frappe/frappe.git frappe-bench
Traceback (most recent call last):
2: from /usr/bin/bench:5:in <main>' 1: from /usr/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in require’
/usr/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require’: cannot load such file – bundler (LoadError)

Try this.
bench init frappe-bench --frappe-branch develop --frappe-path https://github.com/frappe/frappe.git

Traceback (most recent call last):
2: from /usr/bin/bench:5:in <main>' 1: from /usr/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in require’
/usr/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require’: cannot load such file – bundler (LoadError)

getting bench not install errror

Step 10 Install Bench

Bench is a command line utility to install, manage multiple sites and manage the ERPNext application on a Unix-based system.

git clone https://github.com/frappe/bench bench-repo

sudo pip install -e bench-repo

Step 11 Create a new bench

The init command will create a bench directory with frappe framework installed.

bench init --frappe-branch master --frappe-path https://github.com/frappe/frappe.git frappe-bench

already went through these step still getting error

step 1: create one folder as per project name using command mkdir folder_name.

step 2: Create vitual environment in new folder using command for version-12=> virtualenv -p /usr/bin/python3 .

Create vitual environment in new folder using command for below version-12=> virtualenv -p /usr/bin/python2 .

step3: Acitvate source using command- source ./bin/activate

step4: clone the code from github =“https://github.com/frappe/bench.git
using command git clone -b master https://github.com/frappe/bench.git bench-repo

step 5: install bench repo package using:- pip install -e bench-repo
step 6: install frappe framework using command:-
bench init --frappe-branch version-12 --frappe-path https://github.com/frappe/frappe.git frappe-bench

same above steps following for below :
but i tried for frappe & ErpNext develop branch same installation steps

i am not fully aware but would like to bit focus on it.

Version 12 is currently master branch. Develop branch is v13.

please install first 12 then switch it from 12 to 13

bash: /usr/bin/bench: No such file or directory

pip install -e bench-repo
run this but when i fire command:"bench init --frappe-branch develop --frappe-path https://github.com/frappe/frappe.git frappe-bench

o/p:bash: /usr/bin/bench: No such file or directory

adduser [frappe-user]
usermod -aG sudo [frappe-user]

pip install --user frappe-user -e bench-repo using the frappe user.